1. Field of the Invention
This invention relates to a mixture of polycyclic aromatic polycarboxylic acids that is substantially insoluble in acetone and substantially insoluble in water and a process for preparing the mixture by treating a carbonaceous material with nitric acid.
2. Description of Prior Art
Treating a carbonaceous material, such as coal, with nitric acid to obtain carboxylic acids is shown in U.S. Pat. Nos. 2,555,410 to Howard, 2,726,262 to Grosskinsky et al., 2,949,350 to Heinze et al., 2,991,189 to Rickert and 3,173,947 to Benning et al. In each of these the acids obtained are said to be water soluble. Creigton et al. in U.S. Pat. No. 3,468,943 are interested in passing coal through a screw conveyor and at spaced apart intervals feeding appropriate quantities of concentrated nitric acid so that it is completely reacted with the coal before the coal arrives at the next nitric acid feed point to obtain humic acids which are said to be partially soluble in sodium hydroxide solution but substantially insoluble in water.